Barometric draft control



Nov. 6, 1945. A. o. DADY BAROMETRIC DRAFT CONTROL 3 Sheets-Sheet 1 Filed Aug. 1, 1942 [III/6221b) Off/1w" 0 Dag y A. Q. DADY BAROMETRIC DRAFT CONTROL Filed Aug. 1, 1942 3 Sheets-Sheet 2 w wqy Nov. 6, 1945.

Nov. 6, 1945. A. '0. DADY BAROMETRIC DRAFT CONTROL Filed Aug. 1, 1942 3 Sheets-Sheet 3 law/2X02" Uri/aura Dag y b r. V

Patented Nov. 6, 1945 j BAROMETRIC DRAFT CONTROL Arthur 0. Dady, Flossmoor, 11]., assignor to Sears, Roebuck and Co., Chicago, 111., a corporation of New York ApplicationAugust 1, 1942; Serial No 453,295 13 Claims. ('01. 236-45) This invention relates to barometric draft con The purpose of a barometric damper is to provide a means of maintaining a. uniform overfire draft in the combustion chamber of a heating dev1ce such as a boiler or a'warm air furnace, therebytending to promote a uniform rate of combustion and tominimize loss of heat through the stack through excessive draft.

, The general form of such barometric dampers is that of a pivoted shutter mounted in a frame in such a way that increase of draft in the stack tends to open-the shutter, admitting air from the furnace room to the stack, while a decrease of draft in the stack tends 'to close the shutter so that a greater portion of the total .air flow is throughthe fire.

i The best location for the barometric damper varies with the conditions of the installation, but in every case it is placed either in the smoke pipe leading to the chimney or in the base of the chimney itself so that it provides a parallel path for air from the room to enter the stack, the alternative path being that through the fire.

1 The natural .draft o f a chimney depends upon its height and area, the difference in temperature between the flue gases and the outside air, the temperature of the outside air, the barometric pressure and humidity, and the velocity of the wind, the latter being influenced by nearby objects such as buildings, roofs, trees, hills, etc.

It readily can be seen that manual regulation, such as by turn dampers or check dampers in the smoke pipe, can be correct only for the conditions existing at the time of adjustment. Under other conditions there will be too much or too little draft through the fire and the rate of combustion will be correspondingly too high or too low. To automatically maintain given draft conditions some device responsive to the change in draft must be used.

The usual construction of barometric dampers employs a shutter supported on pivots more or less off center so thatthe air flow past the shutter acts on the sides opposite the axis of the pivotsmore or less unequally depending on the offset of the pivots and the angle the shutter makes with the air stream. Since the air stream exerts opposed torques on the opposite sides of the axis,

usually accomplished by aflixing to the shutter,

an adjustable weight which must be raised against gravity as the shutter opens;

Because of the asymmetrical conditionof the air flow andleakage around the periphery of the shutter the rate of change of position is not a uniform function of the change in intensity of the draft. j i i Two methods are used to insure uniform action: (a) reducing the area on one side of the axis as far as possible to thereby reduce the resistive torque to the lowest practical value, and

(17) providing wings closely fitting the sides of the blade in order to cause the maximum air flow over the edge farthest from the axis where it produces the maximum turning moment.

Since the forces operating the damper are small the maximum sensitivity can only be had by reducing the inertia of the moving parts and the friction of the pivots...

The reduction in inertia is accomplished by using light weight blade construction, obtaining the necessary stiffness by forming the piece rather than by increase in thickness. i

The pivots or their equivalent are the most important part of any barometric damper control. If they are susceptible of deterioration by corrosion or by deformation due to rough handling, the device will soon fail to function.

The troublesfrom these sources which have been inherent in previous designs are avoided by employing my invention, i. e., by replacing the conventional pivot construction by a strained wire suspension anchored both tothe frame and to the blade and acting as a torsion spring. Since there is no rotation about the axis the condition of these supports has no effect on the resistance to turning which is-a function" only of the diameter and modulus of elasticity of the material used. By employing a non-corrosive high strength alloy wire such as stainless steel or bronze a suspension is obtained which will always maintain its original state since it is not dependent on the cleanliness of any coacting parts.

Another advantage of this construction lies in the resulting differential action between the opening and the closing phases. If the wire is clamped with the blade in a closed position then the opening causes a torsion in the spring which resists this opening and delays it. This is desirable since it renders the damper less sensitive to a transitory gust of windwhich would increase the draft.

On the other hand since the wire, when the blade is open, is strained in such a way as to tend to act as 'a closing spring, it causes the damper to close almost immediately on a reduction of draft, thereby preventing a positive draft condition from arising and minimizing the danger of flue gas being forced out of openings in the combustion chamber into the furnace room or into the air circulation system of a warm air furnace.

Further objects and advantages of my invention will appear as the description proceeds.

The invention will be better understood upon reference to the following description and accompanying drawings, in which:

Fig. l is a longitudinal vertical sectional view of one form of my invention, taken as indicated by the line |-|in Fig. 2;

Fig. 2 is a rear elevation taken the line 2-2 in Fig. 1;

Fig. 3 is an enlarged plan sectional view taken as indicated by the line 33 in Fig. 2;

Fig. 4 is a fragmentary plan sectional view of an installation employing my invention;

Figs. 5 and 6 are views similar to Figs. 1 and 2, respectively, but of a modification, Fig. 5 being taken as indicated by the line 55 in Figs. 6 and '7;

Fig. 7 is a front elevation of the modification shown in Figs. 5 and 6;

Fig. 8 is a sectional view similar to Fig. 5 but with the damper blade open;

Fig. 9 is a view taken as indicated by the line 99 in Fig. 5;

Fig. 10 is a ,plan view, partly in section, taken as indicated by the line |0--l I] inFig. 6; and

Figs. 11 and 12 show two additional modifications.

Referring now more particularly to the drawings, I have shown in Fig. 4 a typical installation of a boiler or furnace l 0, smoke pipe provided with a barometric draft control 2 built in as indicated'by accordance with one form of my invention, and

a stack l4.

The smoke pipe has an arm I5 in and by which the draft control I2 is supported. I provide a pan-like frame l6 having a peripheral flange 3 adapted to fit frictionally in the free end IQ of the pipe arm I 5, the flange having an outwardly extending lip 20 to limit the insertion and facilitate removal of the frame and also to provide a smooth end surface 22 for handling. To retain the framerin place I strike inward a portion 23 of the flange l8 and support, thereat a nut 24' in which I thread a screw 25 whose point fits into a depression 21 in the pipe arm l5. When the screw 25 is tight it securely holds the frame in the pipe arm; Backing the screw will enable the frame to be removed from the pipe arm.

The base 28 of the frame has a relatively large draft opening 29 and is provided with wings 36 at the sides of the opening, said wings extending rearwardly toward the smoke pipe II. The bottom 32 of the opening 29 is preferably horizontal, the wings 30 are preferably vertical, and the top 33 of the opening is preferably arcuate in conformity with and adjacent the flange 8 of the frame l6. 7

I The blade suspension shown in Figs. 1 to 3 will nowbe described briefly. Mounted adjacent the bottom 32 of the opening 29 and also adjacent the wings 30 are securing means of any suitable character such as the nut and screw means 34, serving as binding posts for adjustably anchoring the ends 35 of a torsion spring wire 31 which passes through holes 38 in the wings 3|] and serves to pivotally support a damper blade 39 as will appear in detail hereinafter.

The damper blade 39 is constructed in general wire.

conformity with the opening 29 in the frame l6, but is of greater vertical extent so as to provide an upper portion 40 overlapping the upper end 33 of the opening at the rear of the base 28 and a lower portion 4| overlapping the bottom 32 of said opening at the front of said base 28. Reinforcing depressions 42 may be formed in thebla'de. 1

The blade '39 adjacent the lower end 4| thereof is formed with a horizontal rear depression 43 and, riveted thereto as at 44 or otherwise suitably secured, is a channel member 45 having its ends 46 bent rearwardly with its upper and lower flanges 41. The end portions 46 of the channel said web provide abridge engaging spaced portions of the wire 31 inwardly from the holes 49. A counterbalancing threaded member 53 is provided with a horizontal portion 54 passing through a nut 55 and the preferably central Part of the blade depression 43 and the adjacent channel web 5|, and is held from rotating by means of a pin 56 passing through the channel flanges 41 and said horizontal portion 54. The portion 54 has a horizontal hole 51 preferably closer than the free ends of the tongues 50 to the Web 5| and receiving the wire 31. When the anchoring devices 34 are tightened to the desired degree of tension'-an operation which need be performed only at the factorythe wire is held taut and out of a straight line, as may be gathered upon inspection of Fig. 3.

The wire is located adjacent the lower end of the blade 39 (Fig, 1) the blade being mounted so that when in closed position as shown it is Somewhat inclined upward and inward, tending to swing inward (to the left, Fig. 1) to an open position. This motion of the blade is resisted by a counterbalance provided by a threaded extension 66 of the bar 53, carrying an adjustable counterweight nut 6|, and also by the pivoting wire, which becomes twisted by such motion, due to the fact that the anchored end portions of the wire are maintained in fixed positions while the intermediate portion of the wire, being spaced from the axis of the end portions, rotates about said axis. The wire is preferably of high strength and non-corrosive so as to always maintain its original state; and acts as a torsion spring whose resistance to the opening and assistance to the closing of the blade are not at all opposed by friction of rotating parts but depend solely on the diameter and modulus of elasticity of the The wire thus delays the opening of the blade, rendering the blade less sensitive to a transitory gust of wind which would objectionably increase the draft, and also causes the open blade to close almost immediately on a reduction in draft, thereby preventing a positive draft condition from arising and minimizing the danger of flue gas being forced out of openings in the combustion chamber into the furnace room or the air circulation system of a warm air furnace.

To eliminate noise, a felt or other suitable buffer button 63 is secured as at 64 to the frame in a position to be engaged by the lower part of the blade. The form and location of the part 63 may be varied as desired.

In accordance with the form of my invention shown in Figs. 5 to 10, a modified counterbalance and pivot suspension may b employed, using, if

desired. the same frame I6 and a blade 61 similar to the blade 39 but carrying a fixed'counterweight 68 spot-welded as at '69 or otherwise suitably connected to the blade.

, The modified pivot suspension may comprise a relatively stiff high strength non-corrosive spring wire 10 passing through holes H in the frame wings 30 and holes 12 in the end flanges "of a bridge 14 spot-Welded as at 15 or otherwise suitably mounted at the bottom of the blade 81, and is intermediately bowed as at 1B and normally in the same plane as its bent-down ends 11, which preferably are further bent as at 11c into engagement with the frame l6, preventing longitudinal displacement of the wire. The bridge may have struck-out tongues or lugs 14a engaging the bowed portion 16. Opening movement of the blade swings the bowed portion 16 into a different plane relative to the remainder of the spring, as shown in Fig. 8, producing a twist in the relatively anchored end portions 11b through the holes I I. Upon closing movement of the blade the bowed portion 16 returns to its normal plane (Fig. Thus the spring resists opening and assists closing of the blade 61 and affords the other advantages explained above.

The modified counterblance may include a strap 18 spot-welded or otherwise suitably secured at 19 as to the fixed counterweight 68 or directly to the blade. if desired, and extending downward and forward. The strap 18 is adapted to adjustably receive a counterbalance weight assembly 811 which may comprise a plurality of small plates 8| spot-welded or otherwise suitably connected together and to a sheet metal wrapper or envelope 82 provided with a thumb screw 83 between which and the Wrapper any selected part of the strap 18 may be clamped.

Another strap 85 spot-welded as at 8B or otherwise suitably fixed to the counterweight 68, or other suitable part moving with the blade 61, extends forward as at 81 and then down and rearward, clear of the lower part of the frame, terminating as at 88 well to the rear and carrying another counterbalance weight assembly 80.

A nice counterbalancing of the blade at the desired normal draft opening may be obtained by adjustment of the weights 80.

In accordance with another form of the invention, shown in Fig. 12, I may provide a blade 90 similar to those above described butmounted on the frame 9| by means of leaf springs 92 which may be riveted or spot-welded as at 94 or otherwise suitably attached to the blade and frame, the springs being preferably corrosion-resistant and relatively light so as to offer the requisite light resistance to opening of the blade by the draft. With this construction the blade may be simpler than those above described since the channel bar is not needed.

In another form (Fig. 11) the springs could be of wire or similar form as shown at 96, having one or more coils 91 and having their ends 98 riveted as at N10 or otherwise suitably attached to the blade 90 and frame 9|.

Any suitable counterbalancing mechanism, such as that above described, may be employed with the forms shown in Figs. Hand 12.

Various modifications coming within the spirit of my invention may suggest themselves to those skilled in the art, and hence I do not wish to be limited to the specific form shown or uses mentioned, except to the extent indicated in the appended claims, which are to be interpreted as broadly as the state of the art will permit.

I claim: 1. A barometric draft control comprising means providinga draft opening, a damper blade for said opening, and a spring wire pivotally suspending said blade from said means, said wire having its terminal portions fixed to said means with adjacent end portions of the wire passing through side portions of said blade and having an intermediate portion engaged with an intermediate portion of said blade and out of line with said end portions, whereby swinging of said blade upon said end portions of the wire will stor up torsional energy in said wire.

2. A barometric draft control comprising means providing a draft opening, a damper blade for said opening, and a spring wire under tension and pivotally suspending said blade from said means, said wire having its terminal portions fixed to said means with adjacent end portions of the Wire passing through side portions of said blade and having an intermediate portion engaged with an intermediate portion of said blade and out of line with said end portions, whereby opening of said blade by swinging upon said end portions of the wire will store up torsional energy in said wire.

3. A barometric draft control comprising means providing a draft opening, a damper blade for said opening, said means and blade having rearwardly extending portions with horizontally alined. holes, said blade having intermediate its sides and at each side of the vertical axis thereof a member extending rearwardly beyond the axis of said holes, said blade having a rearwardly extending part intersecting both of said axes, and provided with a hole alined with the aforesaid holes, a spring wire passing through said holes and engaged with said members rearwardly of the axis of said holes, and means anchoring the ends of said wire to the first-mentioned means.

4 A barometric draft control comprising means providing a draft opening, a damper blade for said opening, said means and blade having rearwardly extending portions with horizontally alined holes, said blade having intermediate its sides and at each side of the vertical axis thereof a member extending rearwardly beyond the axis of said holes, said blade having a rearwardly extending part intersecting both of said axes, and provided with a hole alined with the aforesaid holes, a spring wire passing through said holes and engaged with said members rearwardly of the axis of said holes, and means anchoring the ends of said wire to the first-mentioned means under the desire degree of tension.

5. A barometric draft control comprising means providing a draft opening, a damper blade for said opening, said means and blade having rearwardly extending portions at the sides and adjacent the lower end of said opening, said portions having horizontally alined holes, a spring wire passing through said holes and having an intermediate portion engaged with the blade and out of line with said holes, and means anchoring the ends of said wire to the first means.

6. A barometric draft control comprising means providing a draft opening, a damper blade for said opening, said means and blade having rearwardly extending portions at the sides and adjacent the lower end of said opening, said portions having horizontally alined holes, a spring wire including straight portions of substantial length passing through said holes and having an intermediate portion out of line with said straight portions, means anchoring the ends of said wire to the first means, means anchoring the intermediate portion to the blade, and adjustable counterbalancing means for said blade.

'7. A barometric draft control comprising means'providing a draft opening, a damper blade for said opening, and a hinge connection between said blade'and said means, said hinge connection including pintle means, the entire pintle means of said hinge connection consisting of a single member in the form of a spring torsion wire having spaced portions non-rotatably engaged with the first-mentioned means and said blade and between said portions being unconstrained against rotation, the first mentioned means and said blade having aligned pivot openings, and said wire between said portions passing through said openings to establish a pivot relation between said first mentioned means and said blade, whereby said wire between saicf portions is torsionally energized by pivotal movement of said blade in one direction and thereupon yieldingly urges said blade in the opposite direction.

8. A barometric draft control comprising means providing a draft opening, a damper blade for said opening, and a string torsion wire pivotally suspending said blade from said means, said wire having its terminal portions non-rotatably engaged with said means with adjacent end portions of the wir passing through said blade and having an intermediate portion out of line with said adjacent end portions and non-rotatably engaged with said blade, said wire between said portions thereof being relatively free and capable of being twisted to a substantialextent within the elastic limit thereof whereby swinging of said blade upon said adjacent end portions of the wire blade upon said adjacent end portions of the wire will store up torsional energy in said wire.

10. A barometric draft control comprising means providing a draft opening, a'damper blade for said opening, and a spring torsion wire under tension and pivotally suspending said blade from said means, said wire having its terminal portions non-rotatably engaged with said means with adjacent end portions of the wire passing through said blade 'and having an intermediate portion out of linewith said adjacent end portions and nonrotatably engaged with an intermediate portion of said blade, said wire between said portions thereof being relativelyfree and capable of being twisted to a substantial extent within the elastic limit thereof, whereby swinging of said blade upon said adjacent end portions will store up torsional energy in said wire. l

11. A barometric draft control comprising means providing a draft opening, a damper blade for said opening, said means and blade having horizontally aligned holes, and a spring torsion wire passing through said holes, said wire having an intermediate portion non-rotatably engaged with said blade eccentrically of theaxis' of said holes, said wire having end portions non-rotatably engaged with said means.

12. A barometric draft control comprising means providing a draft opening, a damper blade for said opening, said means and blade having horizontally aligned holes, a spring wire passing through said holes and having an intermediate portion substantially stationarily engaged with said blade eccentrically of the axis of said holes, and means anchoring the ends of said wire to the first-mentioned means under the desired de:- gree of tension.

13. A barometric draft control comprising means providing a draft opening, a damper blade for said opening, said means and blade having rearwardly extending portions at the sides and adjacent to the lower end of said opening, said portions having horizontally aligned holes, and a spring torsion wire passing through said holes and having an intermediate portion non-rotatably engaged with the blade and out of line with said holes, the ends of said wire being non-rotatably engaged with said means.

ARTHUR O. DADY. 

